tolong di jawab ya no 1-3 please

no.1
h =(760-x).10
1200m =(760-x).10
760-x=1200÷10
x=760-120
x=640mmHg

no.2
dik. x= 6.5cmHg = 65mmHg
h=(760-65).10
h=6950m

no.3
P1.V1=P2.V2
P1.20=380.5
P1=1900÷20
P1=95Pa